How do you choose the "3D View Full" workspace?
To make your viewport size bigger you can try CTRL + Space or CTRL + ALT + Space.
If you want to create a workspace that has a big viewport:

Click the '+' button to the right of the scripting tab(assuming you haven't added or removed workspaces)
In the general section choose 'Layout'

Optional: You can rename the workspace by double-clicking on the 'Layout.001' tab

Start collapsing all the windows except the 3D viewport. This is done by moving your cursor to an intersection of 2 windows so that it changes to a '+' sign, then by dragging towards one of the windows.


Do this for all the ones you don't want.